1. Field of the Invention
The present invention relates generally to robotic media storage library systems, and more specifically to a redundant system that includes a plurality of independent robots in the form of robotic pods.
2. Background of the Invention
The current enterprise class library system contains multiple independent robots for concurrently manipulating multiple media cartridges. The library system comprises an array of media storage cells and media cartridge players. A system of rails is used to guide robotic pods through all of the locations on the array.
Fixed guide wheels on a robot rolling on tracks are subject to skidding when the robot changes its direction of travel. This skidding will result in increased noise and wear on the robot wheels. The problem is compounded as the load on the wheels increases.
Therefore, it would be desirable to have a method for reducing noise and wear on the wheels by using a steering mechanism to accommodate changes in the travel direction of the storage library robots.
The present invention provides a steering mechanism for a track-mounted robot. A robot chassis is driven on a track in a longitudinal direction by a pair of drive wheels that are axially fixed to the chassis and connected to drive motor via a belt. The drive wheels are held tightly to the track by a single axially parallel cam follower wheel located between the drive wheels on the opposing side of the track. The cam follower wheel is spring loaded via a linear slider connected to the chassis, and its motion is restricted to move perpendicular to both drive wheel axes. This spring loaded cam follower wheel and slider assembly squeezes the track between the two drive wheels and cam follower wheel.
The steering mechanism comprises fixed upper guide wheels, and spring loaded lower guide wheels that are attached to yokes that pivot around the drive wheels. The upper guide wheel on each yoke is axially fixed to each yoke and rolls along the track on the surface adjacent to the track surface that the drive wheels roll against. The lower guide wheel is attached to the yoke with a pivoting arm and rolls along the opposing track surface from the upper guide wheel. The pivoting arm of the lower guide wheel is spring loaded toward the upper guide wheel, which squeezes the track between the guide wheels. The pivot action of the yokes allows the guide wheels to maintain full contact with the track and steer tangent to the direction of motion as the robot traverses straight and curved portions of the track. Linkage components attach the yokes to the cam follower wheel, which follows the cam surface of the track in order to force the proper angle of steering for the guide wheels.